Extrusion die



May 30, 1933. B TREBES 1,911,858

EXTRUS ION DI E Filed July 1931 INVENTOP B. M A. TPEBES srfigk/Jw ATTORNEY Patented May 30, 1933 UNITED STATES NT OFFICE:

BRUNO M. A. TREBES, or BEBWYN, ILLINOIS, ASSIGNOR T ELL TELEPHONE nAno naromns, INCORPORATED, on NEW YORK, N. Y.,'A CORPORATION or'nnw Yoaxi f EXTRUSION DIE 7 Application filed July 7, 1931, Ser'al No. 549,171, and in Great Britain December 3, 1930.

This invention is an improvement in 'or modification of the arrangement disclosed in applicants Patent 1,859,901, granted May 24, 1932.

In this patent, apparatus for extruding insulating material upon cores for applying the insulating material in a plurality of layers is disclosed. This apparatus comprises a number of die members of successively increasing diameters all having their exit orifices substantially in the same plane taken transversely of the core. The object of the prior arrangement was to obtain a satisfactory application of insulating material notwithstanding any slight fiexure of the cable immediately after leaving the dies.

It has been found, however, that the above arrangement is not altogether satisfactory but that still further improved results can be obtained, in accordance with the present invention, oy extending the central nozzle from which the core emerges a. short distance beyond the plane of the exit orifices of the other die members. The extension is normally only a matter of a few millimeters but it serves as a protector for the soft coating of equalizing medium already on the core at the place of application of the several layers of insulating material. By this means, the soft coating is protected against distortion by any eddy cur rents in the insulating material which are set up. even with the stream line arrangement described in the patent referred to.

The invention will be readily understood with reference to the accompanying drawing in which,

Fig. 1 is a sectional elevation of an arrangement according to the invention,

2 is a sectional view of the die block shown in the arrangement shown in Fig. 1 through line 22 thereon.

In Fig. 1 of the drawing is shown an electrical conductor 1 passing through an extrud ing head for the purpose of being covered with three layers of insulating material. The

extruding head comprises a nozzle 2 screwed into the pipe 3 in which, as described in the patent referred to, pressure equalizing material is applied under pressure. Surrounding the nozzle 2 are dies 4 and 5 having exit orifices of successively increasing diameter and thefinal sizingdie 6. The dies-4 and 5. consist of nozzle-like members screwed onto a: permanent supporting member 7 carried. on the aforementioned end of the tube3 and the three orifices 8, 9, 10, formed between the" nozzle 2 and the sizing die 6, lie in thesame plane while the nozzle 2 itself extends in.

advance of thisplane for a distance of a few millimeters depending on the diameters of the insulating layer to be applied'to the core.

In extruding thermoplastic insulation ofdiameters from to mm. at a speed of 300 meters per hour, it was foundby experi-' mentation that the optimum. length of the extension of the tip of'the nozzle 2 is between 2 and 3 mm. The length. of'the extension of the tip required to produce the-best results under other conditions may be determined by experimentation in accordance with the Scope of this invention. It is believed that in general the extension of the tip required for insulatingca-ble conductors of all ordinary and usual sizes will not diifer very much from the one specified above.

The construction of Y the permanent supporting member 7 is clearly illustrated in Fig. 2. It consists as shown of a casting formed or secured on the end of the tube 3 and comprising cross members 11 serving to maintain ring members 12 and 13- on which the die members 4 and 5 are screwed in correct spaced relation.

The various passages leading to the three exit orifices 8, 9 and 10 are stream-lined as described in the above mentioned patent, the

cross members 11 of the extrusion head also pose of varying the thickness of the layer of the insulating material applied to the cable, or for any other purpose.

It will readily be understood that the use 5 of the extending nozzle 2 is not restricted to an embodiment in an extrusion head in which the die members are screwed on to a permanent member as described above, but the head.

may be formed in any desired workmanlike 1o manner, such as entirely by casting, which is within the scope of the appended claims.

What is claimed is:

1. An extrusion die of the type which is adapted to apply simultaneously a plurality of layers of plastic material to a central core substance, the die comprising in combina-* tion, a central orifice'throughwhich the core substance passes, and a plurality of sur- M V rounding concentric orifices, the central orifice extending outward a short distancebeyond the plane of the surrounding orifices.-

, 2. An extrusion die of the type which is adapted to apply simultaneously a plurality of layers of plastic material to a central core substance, the die comprising in combination,

a central orifice through which the core substance passes, and a plurality of surrounding concentric orifices, the central orifice extending outward a short distance beyond the so plane of the surrounding orifices by a'length which is not less than two and one half millimeters and which is not more than three millimeters. 1 V

In witness whereof, I hereunto subscribe my name this 30th day of June, 1931. i

BRUNO M. A. TREBES. 

